This invention relates to a method for the safe disposition of alkali metals. It is particularly applicable to the disposal of sodium, potassium or alloys of these metals that have been employed in nuclear reactor coolant systems.
In the past small quantities of highly reactive alkali metals were easily eliminated by reaction with water to form alkali metal hydroxides and hydrogen gas. The hydrogen gas was quickly diluted with air and dispersed while the metal hydroxide could be retained or diluted with water for disposal.
Large quantities of alkali metals have been used in recent years within liquid metal cooled nuclear reactors. Such reactors, often cooled with liquid sodium or liquid sodium potassium alloy (NaK), contain extremely large volumes of these highly reactive metals. The disposal of such large quantities of these materials presents previously unthoughtof problems due to their highly exothermic reactions with water and resulting generation of hydrogen gas. Where the liquid metal coolants may be contaminated with radioisotopes, such reactions become even less attractive as a disposal method. In addition, dilution with large volumes of water is undesirable if the waste product must be stored and shielded.
In copending patent application Ser. No. 624,030 filed Oct. 20, 1975, by Lewis, alkali metals are reacted with water in caustic solution with steam added to dilute evolved H.sub.2 gas. Although this method is an improvement over other prior processes, hydrogen gas evolution, the volume of waste products and the possible presence of radioactive material remain troublesome.